In 2012 there were 357 million cases of sexually transmitted infections in the world. In Indonesia in 2016 as many as 61 thousand cases, West Java was the highest rank of STI in 2012 In 2016 the highest prevalence of STIs was gonorrhea 3430 cases 1. Preliminary Study in December 2018 counseling guidance teacher stated that most of the knowledge of high school students did not yet understand the epidemiology of sexually transmitted infections (STIs) and LGBT. It is feared that students do not know the preventive risk of transmitting sexually transmitted infections and LGBT behavior. To determine of knowledge of Senior High School (SMAN) 2 Singaparna students about the epidemiology of STIs, risk factors for STIs and the danger of LGBT. observational study with a descriptive research design with qualitative methods. The sample of this study was students with a purposive sampling of 29 Senior High School Students in January 2019. Data collection using questionnaires and indepth interviews. The analysis used results of interviews and open questionnaires. Knowledge of Senior High School (SMAN) 2 Singaparna students about the epidemiology of STIs, students only know the STI disease agent, which is a virus. Risk factors that are known to students are behavior, sexual deviation and blood transfusion without screening. STI classification that students say the STI classification is HIV / AIDS. the majority of students mention the length of LGBT but some students who cannot mention the impact of LGBT and prevention LGBT.